Polymer mixture comprising polyphenylene ether, sterically hindered amine and epoxy compound and articles manufactured therefrom

ABSTRACT

The invention relates to polymer mixtures which comprise a polyphenylene ether, a sterically hindered amine, an epoxy compound, and a salt of a fatty acid. The polymer mixtures according to the invention have a good stability against discoloring by light.

This is a division of application Ser. No. 07/256,936, filed on Oct. 13,1988 now U.S. Pat. No. 5,045,578.

The invention relates to a polymer mixture comprising the followingconstituents:

A. a polyphenylene ether or a mixture of a polyphenylene ether and an,optionally rubber-modified, polystyrene,

B. a sterically hindered amine, and

C. an epoxy compound.

The invention also relates to articles formed from the polymer mixtureaccording to the invention.

Polymer mixtures which comprises a polyphenylene ether, optionally mixedwith a styrene polymer, a sterically hindered amine and an epoxycompound, are known from JP-A-60/149646. These known polymer mixturehave a good light fastness.

The invention provides polymer mixtures which, compared with theabove-mentioned known polymer mixtures, have an improved light fastness.

The polymer mixtures according to the invention are characterised inthat the polymer mixture comprises 0.1-10 parts by weight of a salt of afatty acid (constituent D) per 100 parts by weight of constituent A.

U.S. Pat. No. 4,442,250 described polymer mixtures which comprise asterically hindered amine as a light stabiliser. The examples of thisapplication describe polymer mixtures which comprise a polyolefin, asterically hindered amine and calcium stearate. The calcium stearate ispresumably used as a lubricant to improve the processibility.

The polymer mixture according to the invention preferably comprises zincstearate as constituent D.

The polymer mixture according to the invention is preferably composed sothat it contains per 0.1-5 parts by weight of consituent B, 0.1-5 partsby weight of constituent C, 0.1-5 parts by weight of constituent D and100 parts by weight of constituent A.

The polymer mixture according to the invention preferably comprises aheterocyclic sterically hindered amine, for example, a compound having apiperidyl derivative, as constituent B.

In addition to the constituents mentioned hereinbefore, the polymermixture according to the invention may optionally comprise conventionaladditives, for example, glass fibres, agents to improve the impactstrength, agents for thermal stabilisation, agents to improve theflame-retarding properties.

The polymer mixture according to the invention comprises at any rate oneor more constituents selected from the groups of constituents to bementioned hereinafter:

A. a polyphenylene ether or a mixture of a polyphenylene ether and an,optionally rubber-modified, polystyrene,

B. a sterically hindered amine,

C. an epoxy compound, and

D. a salt of a fatty acid.

The polymer mixture according to the invention may moreover compriseconventional additives as constituent E.

A. Polyphenylene ether, mixture of polyphenylene ether and an,optionally rubber-modified, polystyrene.

Polyphenylene ethers are generally known polymers. Any polyphenyleneether know per se may be used in the polymer mixtures according to theinvention. An elaborate list of suitable polyphenylene ethers is to befound, for example, in WO 87/00540.

Particularly suitable are poly(2,6-dimethyl-1,4-phenylene)ether,poly(2,6-diethyl-1,4-phenylene)ether,poly(2-methyl-6-ethyl-1,4-phenylene)ether. It is also possible to usecopolymers, for example, copolymers which comprise units derived from2,3,6-trimethylphenol and from 2,6-dimethylphenol.

Mixtures of polyphenylene ethers and an optionally rubber-modifiedpolystyrene are also known per se. For this purpose reference may bemade to U.S. Pat. No. 3,383,435; U.S. Pat. No. 4,128,602; U.S. Pat. No.4,128,603; U.S. Pat. No. 4,128,604 and U.S. Pat. No. 3,943,191.

The mutual weight ratio between the polyphenylene ether and thepolystyrene may be varied between wide limits.

B. Sterically hindered amine.

Sterically hindered amines are a group of compounds known per se whichare generally used for stabilising polymers. Particularly suitable arethe commercially available products. These products generally comprisecompounds having groups derived from piperidine. Such compounds andtheir use as stabilisers for polymers are described, for example in U.S.Pat. No. 4,086,204; U.S. Pat. No. 4,233,412; U.S. Pat. No. 4,442,250 andEP-A-0172138.

C. Epoxy compounds

Epoxy compounds are compounds which comprise an epoxide group. Suitableepoxy compounds are, for example, compounds of the formula: ##STR1##wherein R, R¹, R² and R³ represent an organic group.3,4-Epoxyhexahydrobenzyl-3,4-epoxyhexahydrobenzoate and triglycidylisocyanurate are to be preferred.

D. Salts of fatty acids.

The polymer mixtures according to the invention comprise one or moresalts of fatty acids. As fatty acids may be used unsaturated andsaturated acids. These acids may comprise aromatic groups.

The salts may also be derived from alkali metals and alkaline earthmetals. Salts derived from other metals, for example, Mn, Fe, Zn, mayalso be used. Zinc salts are to be preferred.

Examples of suitable salts are zinc stearate, zinc oleate, zinc laurate,zinc palmitate, zinc behenate, zinc arachinate.

E. Conventional additives

In addition to the constituents mentioned hereinbefore, the polymermixture according to the invention may comprise one or more additives.Examples of suitable additives are dyes, pigments, reinforcing fibres,for example, glass fibres, agents to improve the impact strength, agentsto improve the stabilisation and agents to improve the flame-retardingproperties.

Vinylaromatic diene diblock or triblock copolymers are preferably usedas agents to improve the impact strength. These block copolymers may bepartially hydrogenated.

Phosphorus-containing compounds may be used as thermal stabilisers.Phosphate esters are frequently used as flame-retardants.

The polymer mixture according to the invention may be prepared in theusual manner. It is prefarably prepared by compounding the desiredconstituents together in an extruder and processing them to pellets.Articles can be obtained from the resulting pellets, for example, byextrusion or injection-moulding.

The invention will be described in greater detail with reference to thefollowing specific examples.

EXAMPLE I

Various polymer mixtures were prepared having a composition as describedhereinafter. The said constituents were compounded in an extruder andprocessed to pellets. Test plates were manufactured from the pellets byinjection moulding. A part of the resulting plates were exposed to lightunder filtered UV light (Xenon lamp with window glass filter) for 700hours. The change in colour of the exposed plates was determined incomparison with a non-exposed plate manufactured from the same polymermixture. The changes in colour were measured and calculated according toCIELAB (DIN 6174). The discoloring is indicated in the table hereinafteras Delta E_(ab*) value. The discoloring is stronger according as thesaid value is higher.

All polymer mixtures always comprise 35 parts by weight ofpoly(2,6-dimethyl-1,4-phenylene)ether, having an intrinsic viscosity of0.47 dl/g, measured in CHCl₃ at 25° C., 65 parts by weight ofhigh-impact polystyrene, 10 parts by weight of a mixture of organicphosphate esters, 0.8 parts by weight of stabilisers, 5 parts by weightof titanium dioxide, and 2 parts by weight of a sterically hinderedamine. The following commercially available products of Ciba Geigy wereused as a sterically hindered amine: CHIMASORB® 944; Tinuvin® 770 andChimasorb® P 944. These are invariably products which comprise groupsderived from piperidine.

Nearly all the polymer mixtures comprise an epoxy compound, namelytriglycidyl isocyanurate or 3,4-epoxyhexahydrobenzyl-3,4-epoxyhydrobenzoate in a quantity as indicated in thetable hereinafter. Approximately half of the polymer mixtures comprise asalt of a fatty acid, namely zinc stearate, in a quantity of 0.5 partsby weight. The balance did not contain any zinc stearate.

The composition and the resulting Delta E_(ab*) values are recorded inthe table hereinafter.

                  TABLE                                                           ______________________________________                                                               Parts by                                               Hindered  Epoxy compound                                                                             Delta E.sub.ab*                                        amine     (parts by weight)                                                                          zinc stearate                                                                            value                                       ______________________________________                                        Chimasorb 944          0          8.4                                                 TGI    (0.6)   0          5.6                                                 TGI    (0.6)     0.5      4.3                                                 TGI    (1.3)   0          5.3                                                 TGI    (1.3)     0.5      3.4                                                 EBEB   (0.9)   0          7.2                                                 EBEB   (0.9)     0.5      4.9                                                 EBEB   (1.9)     0.5      4.7                                         Tinuvin 770                                                                             --           0          6                                                   TGI    (0.6)   0          4.7                                                 TGI    (0.6)     0.5      3                                                   TGI    (1.3)   0          4.0                                                 TGI    (1.3)     0.5      2.8                                                 EBEB   (0.9)   0          5.8                                                 EBEB   (0.9)     0.5      4.1                                                 EBEB   (1.9)   0          5.2                                                 EBEB   (1.9)     0.5      3.9                                         Chimasorb P944                                                                          --           0          7.7                                                 TGI    (0.6)   0          5.8                                                 TGI    (0.6)     0.5      4                                                   TGI    (1.3)   0          4.2                                                 TGI    (1.3)     0.5      3.9                                                 EBEB   (0.9)   0          8.1                                                 EBEB   (0.9)     0.5      5.5                                                 EBEB   (1.9)   0          5.4                                                 EBEB   (1.9)     0.5      6.2                                         ______________________________________                                         TGI = Triglycidyl isocyanurate                                                EBEB = Epoxyhexahydrobenzyl3,4-epoxyhexahydrobenzoate                    

It will be obvious from the results shown that polymer mixtures which,in addition to the amine and the epoxy compound, comprise a zincstearate have a better light fastness.

We claim:
 1. A polymer mixture which comprises:a) at least onepolyphenylene ether, or a mixture of polyphenylene ether and polystyreneresin; b) a sterically hindered amine; c) and epoxy compound; d) a saltof a fatty acid, present at a level of 0.1-10 parts by weight per 100parts by weight of constituent A; and e) at least one additive selectedfrom the group consisting of dyes, pigments, reinforcing fibres, thermalstabilization agents, and flame retardants.
 2. The polymer mixture ofclaim 1, wherein the polyphenylene ether is selected from the groupconsisting of poly(2,6-dimethyl-1,4-phenylene)ether,poly(2,6-diethyl-1,4-phenylene)ether,poly(2-methyl-6-ethyl-1,4-phenylene)ether; and copolymers comprisingunits derived from 2,3,6-trimethylphenol and 2,6-dimethylphenol.
 3. Thepolymer mixture of claim 1, wherein constituent (b) is a heterocycliccompound.
 4. The mixture of claim 3, wherein constituent (b) is apiperidyl derivative.
 5. The polymer mixture of claim 1, wherein theepoxy compound has the formula ##STR2## wherein each R, R¹, R² and R³represents an organic group.
 6. The polymer mixture of claim 5, whereinthe epoxy compound is either3,4-epoxyhexahydrobenzyl-3,4-epoxyhexahydro-benzoate or triglycidylisocyanurate.
 7. The polymer mixture of claim 1, wherein constituent (D)is a salt derived from a metal selected from the group consisting ofalkali metals, alkaline earth metals, manganese, iron, and zinc.
 8. Thepolymer mixture of claim 1, wherein the polystyrene resin isrubber-modified.
 9. The polymer of claim 1, wherein the reinforcingfibers are glass.
 10. the polymer mixture of claim 1, wherein thestabilizer is a phosphorus-containing compound.
 11. The polymer mixtureof claim 1, wherein the flame retardant is a phosphate ester. 12.Articles formed from the polymer mixture of claim 1.